SECONDARY INTERCONNECT FOR FUEL CELL SYSTEMS
A fuel cell system is provided. The fuel cell system may be a segmented-in-series, solid-oxide fuel cell system. The system may comprise a fuel cell tube and a secondary interconnect. The fuel cell tube may comprise a substrate, a fuel channel, a first and second electrochemical active fuel cell, a primary interconnect, and an electrochemically inactive cell. The substrate may have a major surface. The fuel channel may be separated from the major surface by the substrate. The first and second electrochemically active fuel cells may be disposed on the major surface, and may comprise and anode, a cathode, and an electrolyte disposed between the anode and the cathode. The primary interconnect may electrically couple the anode of the first electrochemically active fuel cell to the cathode of a second electrochemically active fuel cell. The electrochemically inactive fuel cell may be disposed on the major surface and comprise a conductive layer electrically coupled to the second electrochemically active fuel cell. The secondary interconnect may be coupled to the conductive layer of the electrochemically inactive cell. The electrochemically inactive cell is configured to inhibit the migration of hydrogen from said fuel channel to the secondary interconnect.
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This application is related to concurrently filed and co-pending U.S. application Ser. No. ______, filed Nov. 17, 2017, entitled “Multiple Fuel Cell Secondary Interconnect Bonding Pads and Wires,” bearing Docket Number G3541-00244/FCA12024, with named inventors Gerry Agnew, U.S. application Ser. No. ______, filed Nov. 17, 2017, entitled “Fuel Cell Ink Trace Interconnect,” bearing Docket Number G3541-00245/FCA12023, with named inventors Ed Daum, U.S. application Ser. No. ______, filed Nov. 17, 2017, entitled “Improved Fuel Cell Secondary Interconnect,” bearing Docket Number G3541-00181/FCAG11711, with named inventors Zhien Liu, Rich Goettler, Ed Daum, and Charles, Osborn, and U.S. application Ser. No. ______, filed Nov. 17, 2017, entitled “Improved Fuel Cell Secondary Interconnect,” bearing Docket Number G3541-00246/FCAG11979, with named inventors Zhien Liu, Rich Goettler, the entirety of all these applications is incorporated herein by reference.
GOVERNMENT LICENSE RIGHTS STATEMENTThis invention was made with Government support under Assistance Agreement No. DE-FE0000303 awarded by Department of Energy. The Government has certain rights in this invention.
TECHNICAL FIELDThe disclosure generally relates to fuel cells, such as solid oxide fuel cells.
BACKGROUNDFuel cells, fuel cell systems, and interconnects for fuel cells and fuel cell systems remain an area of interest. Some existing systems have various shortcomings, drawbacks, and disadvantages relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology.
SUMMARYThe disclosure describes secondary interconnects for fuels cells, such as, for example, integrated planar solid oxide fuels cells.
In accordance with some embodiments of the present disclosure, a fuel cell system is provided. The fuel cell system may be a segmented-in-series, solid-oxide fuel cell system. The system may comprise a fuel cell tube and a secondary interconnect. The fuel cell tube may comprise a substrate, a fuel channel, a first and second electrochemical active fuel cell, a primary interconnect, and an electrochemically inactive cell. The substrate may have a major surface. The fuel channel may be separated from the major surface by the substrate. The first and second electrochemically active fuel cells may be disposed on the major surface, and may comprise and anode, a cathode, and an electrolyte disposed between the anode and the cathode. The primary interconnect may electrically couple the anode of the first electrochemically active fuel cell to the cathode of a second electrochemically active fuel cell. The electrochemically inactive fuel cell may be disposed on the major surface and comprise a conductive layer electrically coupled to the second electrochemically active fuel cell. The secondary interconnect may be coupled to the conductive layer of the electrochemically inactive cell. The electrochemically inactive cell is configured to inhibit the migration of hydrogen from said fuel channel to the secondary interconnect.
In accordance with some embodiments of the present disclosure, a segmented-in-series fuel cell system is provided. The system may comprise a substrate having a first major surface second major surface, a fuel channel disposed between the first and second major surfaces, wherein the fuel channel is separated from the first and second major surfaces by the substrate, a first and second electrochemically active fuel cells disposed on the first major surface and a third and fourth electrochemically active fuel cells disposed on the second major surface, each of the electrochemically active fuel cells comprising an anode, a cathode, and an electrolyte disposed between said anode and said cathode, a first primary interconnect electrically coupling the anode of the first electrochemically active fuel cell to the cathode of the second electrochemically active fuel cell, a second primary interconnect electrically coupling the anode of the third electrochemically active fuel cell to the cathode of the fourth electrochemically active fuel cell, a first electrochemically inactive cell disposed on the first major surface and a second electrochemically inactive cell disposed on the second major surface, each of the electrochemically inactive cells comprising a conductive layer electrically coupled to at least one of the electrochemically active fuel cells, and a secondary interconnect electrically coupled to the conductive layer of the first and second electrochemically inactive cells, wherein the electrochemically inactive cells are configured to inhibit migration of hydrogen from the fuel channel to the secondary interconnect.
In accordance with some embodiments of the present disclosure, a fuel cell tube is provided. The fuel cell tube may comprise a substrate having a major surface, a fuel channel separated from the major surface by the substrate, at least one electrochemically active cell disposed on the major surface comprising, the electrochemically active cell comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode, an electrochemically inactive cell disposed on the major surface, the electrochemically inactive cell comprising a conductive layer, an electrolyte disposed between said conductive layer and the major surface of said substrate, and a dense barrier disposed between the electrolyte and the major surface of said substrate, and a primary interconnect electrically coupling the anode of the electrochemically active cell and the conductive layer. The tube may further comprise a secondary interconnect comprising palladium electrically coupled to the conductive layer of the electrochemically inactive cell, wherein the secondary interconnect is at least partly buried by a conductive bonding paste.
In one aspect, the disclosure describes a fuel cell system that includes at least a first fuel cell tube and a second fuel cell tube. The first fuel cell tube includes a substrate, a fuel channel, and a first fuel cell formed on the substrate. The substrate separates the first fuel cell from the fuel channel. The first fuel cell includes a cathode, an electrolyte, an anode that is separated from the cathode by the electrolyte. A primary interconnect adjacent the anode electrically couples the anode of the first fuel cell to a cathode conductive layer adjacent to the first fuel cell. A secondary interconnect is formed on and electrically coupled to the cathode conductive layer. The secondary interconnect is configured to electrically couple the first fuel cell tube and the second fuel cell tube. The cathode conductive layer is disposed between the secondary interconnect and an electrolyte or dense barrier that is configured to inhibit the migration of hydrogen from the fuel channel into the secondary interconnect.
In another aspect, the disclosure describes a fuel cell system that includes at least a first fuel cell tube and a second fuel cell tube. The first fuel cell tube includes a substrate, a fuel channel, and a first fuel cell formed on the substrate. The substrate separates the first fuel cell from the fuel channel. The first fuel cell includes a cathode, an electrolyte, an anode separated from the cathode by the electrolyte. A primary interconnect adjacent the anode electrically couples a secondary interconnect conductive layer to the anode. A secondary interconnect is formed on and electrically coupled to the secondary interconnect conductive layer. The secondary interconnect is configured to electrically couple the first fuel cell tube and the second fuel cell tube. The secondary interconnect conductive layer is disposed between the secondary interconnect and an electrolyte or dense barrier that is configured to inhibit the migration of hydrogen from the fuel channel into the secondary interconnect.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views.
Referring to the drawings, some aspects of a non-limiting example of a fuel cell system in accordance with the present disclosure are schematically depicted. In the drawing, various features, components and interrelationships therebetween of aspects of an example of the present disclosure are depicted. However, the present disclosure is not limited to the particular examples presented and the components, features and interrelationships therebetween as are illustrated in the drawings and described herein.
DETAILED DESCRIPTIONAs described above, examples of the present disclosure relate to example secondary interconnects for fuels cells, such as, e.g., solid oxide fuels cells (SOFCs) and integrated planar SOFCs, and the manner in which secondary interconnects are connected to fuel cells and fuel cell tubes.
An electrochemical cell, such as a fuel cell, converts chemical energy into electrical energy and includes an anode, cathode and electrolyte. In some examples, each fuel cell may provide about one voltage depending on the fuel composition. Each cell may generate from around several hundred milliwatts to around several hundred watts of power depending on cell area, cell internal resistance, operating voltage, and the like. To provide higher voltage and generate more power, individual cells may be connected in series through one or more interconnects. Interconnects may be a suitable electronic conductor that allows for the transport electrons from one cell to another.
A primary interconnect may connect a first fuel cell to a second fuel cell on a fuel cell tube or substrate. In an integrated planar SOFC, all active fuel cell layers (e.g., anode, electrolyte and cathode) may be disposed on inert porous ceramic substrate, which may be a flat tube, circular tube, or the like. If the substrate is flat tube, fuel cells may be deposited on both sides of the substrate. A plurality of fuel cells may be disposed on a substrate, wherein each individual fuel cell is connected to at least one adjacent fuel cell through a primary interconnect. This design is also known as a segmented-in-series SOFC.
To form relatively large fuel cell systems having, for example, from combined total power output (heat and electrical) of 1 kilowatt (kW) to 5 kW and larger distributed power generation systems having a total power output of 100 kW to 1 MW, multiple fuel cell tubes may be connected to form a fuel cell bundle, multiple fuel cell bundles may be connected to form a fuel cell strip, multiple fuel cell strips may be connected to form a fuel cell block, and multiple fuel cell blocks may be connected to form a fuel cell generator module. Connecting multiple fuel cell tubes, multiple fuel cell bundles, multiple fuel cell strips, or multiple fuel cell blocks may allow a fuel cell system to generate higher voltage and more power.
In integrated planar SOFCs, the connection between fuel cell tubes may be called a secondary interconnect. The term secondary interconnect may also refer to the connections between fuel cells on opposite sides of the same fuel cell tube. The connections between fuel cell strips, fuel cell bundles, or fuel cell blocks may be called a tertiary interconnect.
As will be described further below, some examples of the disclosure relate to the connection between tubes, or the cell connections between tubes, including, e.g., the cell connection on two sides of the tubes.
Fuel cell systems may include a secondary interconnect at a location on an anode side of a fuel cell tube, for example, by bonding the secondary interconnect to an anode conductive layer (anode current collector, or ACC) with conductive bonding paste and covering the contact point with sealing glass. The sealing glass may provide a gastight barrier to separate the oxidant side (air side) and fuel side (hydrogen flow channel) of the fuel cell system. However, the fuel may have a high fuel flux, e.g., of hydrogen, through the fuel cell components to the secondary interconnect, and the secondary interconnect may comprise a material through which the fuel may readily migrate to the oxidant side of the fuel cell system. This migrated fuel may then combine with the oxidant and burn at or near the surface of the secondary interconnect. Burning of the fuel at or near the surface of the secondary interconnect may result in a microstructural change to the secondary interconnect caused by the formation of localized hot spots. This microstructural change to the secondary interconnect may result in loss of conductivity of the secondary interconnect, as well as loss of mechanical strength or mechanical failure of the secondary interconnect, leading to a less robust product.
To maintain mechanical integrity and electrical conductivity of the secondary interconnect, structures, systems, components and methods may be employed that separate the secondary interconnect from the fuel channel to prevent a hydrogen fuel flux from reaching the secondary interconnect.
Examples of the disclosure are directed to fuel cell systems that inhibit the flux of hydrogen fuel into the secondary interconnect by providing structures, systems, components and methods that prevent the flux of hydrogen to the secondary interconnect. In some embodiments, an electrochemically inactive cell (aka “dummy cell”) may be disposed between the secondary interconnect and the fuel cell system fuel channel Some embodiments of the disclosure are also directed to fuel cell systems that include any one of a dense barrier and an electrolyte, either of which may be configured to inhibit the flow of hydrogen, or another fuel, from the fuel channel into the secondary interconnect.
The fuel cell system 10 includes an oxidant side 18 and a fuel side 20. The oxidant is generally air, but could also be pure oxygen (02) or other oxidants, including, for example, diluted air generated in the fuel cell or by supporting systems, e.g. by having one or more air recycle loops. The oxidant may be supplied to fuel cells 12 from oxidant side 18. During fuel cell 12 operation, the oxidant side 18 may define an oxidizing environment. The oxidizing environment may include oxygen partial pressures of 0.1 to 0.9 bar and 0.2 to 0.6 bar and temperatures of 700 to 1000 degrees centigrade and 800-900 degrees centigrade.
A fuel, such as a reformed hydrocarbon fuel or synthesis gas, is supplied to fuel cells 12 from fuel side 20 via fuel channels (not shown) in porous substrate 14.
Although oxidant (e.g. air) and fuel (e.g., synthesis gas that may be reformed from a hydrocarbon fuel) are described above, it will be understood that electrochemical cells using other oxidants and fuels may be employed without departing from the scope of the present disclosure, such as, for example, pure hydrogen and pure oxygen. In addition, although fuel is supplied to fuel cells 12 via substrate 14, it will be understood that in some examples, the oxidant may be supplied to the electrochemical cells via a porous substrate.
Substrate 14 may comprise a ceramic material having a specific porosity, and may be stable at fuel cell operation conditions and chemically compatible with other fuel cell materials. In some examples, substrate 14 may be a surface-modified material, for example, a porous ceramic material having a coating or other surface modification, such as, for example, being configured to prevent or reduce interaction between fuel cell 12 components and substrate tube.
In each fuel cell, ACC 22 conducts free electrons away from anode 24 and conducts the electrons to the cathode conductive layer 30 of an adjacent cell via primary interconnect 16. Cathode conductive layer 30 conducts the electrons to cathode 28. Primary interconnect 16 is electrically coupled to anode conductive layer 22 and to cathode conductive layer 30.
For SOFCs, primary interconnects are preferably electrically conductive in order to transport electrons from one electrochemical cell to another; mechanically and chemically stable under both oxidizing and reducing environments during fuel cell operation; and nonporous, in order to prevent diffusion of the fuel and/or oxidant through the interconnect. If the interconnect is porous, fuel may diffuse to the oxidant side and burn, resulting in local hot spots that may result in degradation of materials and mechanical failure, reduced efficiency of the fuel cell system, or reduced fuel cell life. Similarly, the oxidant may diffuse to the fuel side, resulting in burning of the fuel. Severe interconnect leakage may significantly reduce the fuel utilization and performance of the fuel cell, or cause catastrophic failure of fuel cells or stacks.
Primary interconnect 16 may be formed of a precious metal, including, for example, Ag, Pd, Au, or Pt, although other materials may be employed without departing from the scope of the present disclosure. For example, it is alternatively contemplated that other materials may be employed, including precious metal alloys, such as Ag—Pd, Ag—Au, Ag—Pt, Au—Pd, Au—Pt, Pt—Pd, Ag—Au—Pd, Ag—Au—Pt, Ag—Au—Pd—Pt, as well as binary, ternary, or quaternary alloys in the Pt—Pd—Au—Ag family, inclusive of alloys having minor non-precious metal additions, cermets composed of a precious metal, precious metal alloy, and an inert ceramic phase, such as alumina, or ceramic phase with minimum ionic conductivity which will not create significant parasitics, such as YSZ (yttria stabilized zirconia, also known as yttria doped zirconia, wherein yttria doping is 3-8 mol %, preferably 3-5 mol %), ScSZ (scandia stabilized zirconia, wherein scandia doping is 4-10 mol %, preferably 4-6 mol %), doped ceria, and/or conductive ceramics, such as conductive perovskites with A or B-site substitutions or doping to achieve adequate phase stability and/or sufficient conductivity as an interconnect, e.g., including at least one of doped strontium titanate (such as LaxSr1-xTiO3-δ, x=0.1 to 0.3), LSCM (La1-xSrxCr1-yMnyO3, x=0.1 to 0.3 and y=0.25 to 0.75), doped yttrium chromites (such as Y1-xCaxCrO3-δ, x=0.1-0.3) and/or other doped lanthanum chromites (such as La1-xCaxCrO3-δ, where x=0.15-0.3), and conductive ceramics, such as doped strontium titanate, doped yttrium chromites, LSCM (La1-xSrxCr1-yMnyO3), and other doped lanthanum chromites. In one example, primary interconnect 16 may be formed of y(PdxPt1-x)-(1-y)YSZ. Where x is from 0 to 1 in weight ratio, and preferably x is in the range of 0 to 0.5 for lower hydrogen flux. Y is from 0.35 to 0.80 in volume ratio, and preferably y is in the range of 0.4 to 0.6.
Anode conductive layer 22 may be an electrode conductive layer formed of a nickel cermet, such as such as Ni-YSZ (e.g., where yttria doping in zirconia is 3-8 mol %), Ni-ScSZ (e.g., where scandia doping is 4-10 mol %, preferably including a second dopant, for example, 1 mol % ceria for phase stability for a 10 mol % scandia-ZrO2) and/or Ni-doped ceria (such as Gd or Sm doping), doped lanthanum chromite (such as Ca doping on A site and Zn doping on B site), doped strontium titanate (such as La doping on A site and Mn doping on B site), La1-xSrxMnyCr1-yO3 and/or Mn-based R-P phases of the general formula a (La1-xSrx)n+1MnnO3n+1. Alternatively, it is considered that other materials for anode conductive layer 22 may be employed such as cermets based in part or whole on precious metal, nickel, or both. Precious metals in the cermet may include, for example, Pt, Pd, Au, Ag, and/or alloys thereof. The ceramic phase may include, for example, an inactive, non-electrically conductive phase, including, for example, YSZ, ScSZ and/or one or more other inactive phases. These ceramic phases may have a coefficient of thermal expansion (CTE) that helps control the combined CTE of ACC 22 to match, or better match, the CTE of the substrate 14 and/or electrolyte 26. In some examples, the ceramic phase may include Al2O3 and/or a spinel such as NiAl2O4, MgAl2O4, MgCr2O4, and NiCr2O4. In some examples, the ceramic phase may be electrically conductive, e.g., doped lanthanum chromite, doped strontium titanate and/or one or more forms of LaSrMnCrO and/or R-P phases of the general formula (La1-xSrx)n+1MnnO3n+1.
Electrolyte 26 may be made from a ceramic material. In one form, a proton and/or oxygen ion conducting ceramic may be employed. In one form, electrolyte 26 is formed of YSZ, such as 3YSZ and/or 8YSZ. In some examples, electrolyte 26 may be formed of ScSZ, such as 4ScSZ, 6ScSz and/or 10Sc1CeSZ in addition to or in place of YSZ. In some examples, other materials may be employed. For example, it is considered that electrolyte 26 may be made of doped ceria and/or doped lanthanum gallate. In any event, electrolyte 26 is substantially impervious to diffusion therethrough of the fluids used by fuel cell system 10, e.g., synthesis gas or pure hydrogen as fuel, as well as, e.g., air or O2 as an oxidant, while still allowing diffusion of oxygen ions or protons.
Cathode conductive layer 30 may be an electrode conductive layer formed of a conductive ceramic, for example, at least one of LaNixFe1-xO3 (such as, e.g., LaNi0.6Fe0.4O3), La1-xSrxMnO3 (such as La0.75Sr0.25MnO3), La1-xSrxCoO3 and/or Pr1-xSrxCoO3 (such as Pr0.8Sr0.2CoO3). In some examples, cathode conductive layer 30 may be formed of other materials, e.g., a precious metal cermet, although other materials may be employed without departing from the scope of the present invention. The precious metals in the precious metal cermet may include, for example, Pt, Pd, Au, Ag and/or alloys thereof. The ceramic phase may include, for example, YSZ, ScSZ and Al2O3, or other non-conductive ceramic materials as desired to control thermal expansion.
Any suitable technique may be employed to form fuel cell system 10 of
A gap may separate anodes 24 of adjacent fuel cells. Similarly, a gap may separate cathodes 28 of adjacent fuel cells. Each fuel cell 12 is formed of an anode 24 and the cathode 28 spaced apart by a portion of electrolyte 26.
Similarly, ACC 22 (also known as an anode conductor film) and CCC 30 (also known as a cathode conductor film) may have respective gaps between adjacent ACCs 22 and CCCs 30. The terms, “anode conductive layer” and “anode conductor film” may be used interchangeably.
In some examples, anode conductive layer 22 has a thickness of approximately 5-15 microns, although other values may be employed without departing from the scope of the present disclosure. For example, the anode conductive layer may have a thickness in the range of approximately 5-50 microns. In some examples, different thicknesses may be used, for example, depending upon the particular material and application.
Similarly, anode 24 may have a thickness of approximately 5-20 microns, although some values may be employed without departing from the scope of the present invention. In some examples, the anode may have a thickness in the range of approximately 5-40 microns. In some examples, different thicknesses may be used, for example, depending upon the particular anode material and application.
Electrolyte 26 may have a thickness of approximately 5-15 microns with minimum individual sub-layer thicknesses of approximately 5 microns. Other thickness values may be employed without departing from the scope of the present invention. For example, the electrolyte may have a thickness in the range of approximately 5-200 microns. In some examples, different thicknesses may be used, for example, depending upon the particular materials and application.
Cathode 28 may have a thickness of approximately 3-30 microns, such as, for example, approximately 5-10 microns. Other values may be employed without departing from the scope of the present invention. For example, the cathode may have a thickness in the range of approximately 10-50 microns. In some examples, different thicknesses may be used, for example, depending upon the particular cathode material and application.
Cathode conductive layer 30 has a thickness of approximately 5-100 microns, although other values may be employed without departing from the scope of the present invention. For example, the cathode conductive layer may have a thickness less than or greater than the range of approximately 5-100 microns. In some examples, different thicknesses may be used, for example, depending upon the particular cathode conductive layer material and application.
The fuel cell system 10 may further comprise a secondary interconnect 34, and conductive bonding paste 36.
It will be understood that
As shown in
As shown in
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Although not shown in
As shown in
In accordance with some embodiments of the disclosure, one or more of electrolyte 26 or dense barrier 32 may be configured to inhibit the migration of hydrogen, or another fuel, from fuel channel 70 into secondary interconnect 34. For example, the and location of one or more of electrolyte 26 or dense barrier 32 with respect to substrate 14, fuel channel 70, or the oxidant side (not shown may inhibit the migration of hydrogen, or another fuel, from fuel channel 70 into secondary interconnect 34 when the electrolyte 26 or dense barrier 32 comprises the above mentioned materials. Also, the density, the porosity, or both of one or more of electrolyte 26 and dense barrier 32 may be configured to inhibit the migration of hydrogen, or another fuel, from fuel channel 70 into secondary interconnect 34. The porosity of electrolyte 26 may be, for example, in the range of less than 20%, or, for example, than 5%. The porosity of dense barrier 32 may be, for example, less than 20%, or, for example, less than 5%. In this way, electrochemically inactive cell 31 of
In accordance with some embodiments, the dense barrier 32, electrolyte 26, or both of the electrochemically inactive cell 31 are gastight (i.e., prohibit the migration of H2) in the vertical direction of
System 10 shown in
System 10 shown in
System 10 shown in
Though
In some examples, secondary interconnect conductive layer 40 may be electrically conductive. For example, secondary interconnect conductive layer 40 may be formed of a precious metal, including, for example, Ag, Pd, Au, or Pt, although other materials may be employed without departing from the scope of the present disclosure. For example, it is contemplated that other materials may be employed, including precious metal alloys, such as Ag—Pd, Ag—Au, Ag—Pt, Au—Pd, Au—Pt, Pt—Pd, Ag—Au—Pd, Ag—Au—Pt, Ag—Au—Pd—Pt, as well as binary, ternary, or quaternary alloys in the Pt—Pd—Au—Ag family, inclusive of alloys having minor non-precious metal additions, ferrochrome alloys, cermets composed of a precious metal, precious metal alloy, and an inert ceramic phase, such as alumina, stabilized zirconia, La2Zr2O7, or a ceramic phase with minimum ionic conductivity which will not create significant parasitics, such as YSZ (yttria stabilized zirconia, also known as yttria doped zirconia, wherein yttria doping is 3-8 mol %, preferably 3-5 mol %), ScSZ (scandia stabilized zirconia, wherein scandia doping is 4-10 mol %, preferably 4-6 mol %), doped ceria, and/or conductive ceramics, such as conductive perovskites with A or B-site substitutions or doping to achieve adequate phase stability and/or sufficient conductivity as an interconnect, e.g., including at least one of LSM, LSC, LNF, PSM, LSF, LSCF, doped strontium titanate (such as LaxSr1-xTiO3-δ, x=0.1 to 0.3), LSCM (La1-xSrxCr1-yMnyO3, x=0.1 to 0.3 and y=0.25 to 0.75), doped yttrium chromites (such as Y1-xCaxCrO3-δ, x=0.1-0.3) and/or other doped lanthanum chromites (such as La1-xCaxCrO3-δ, where x=0.15-0.3), and conductive ceramics, such as doped strontium titanate, doped yttrium chromites, LSCM (La1-xSrxCr1-yMnyO3), and other doped lanthanum chromites.
Secondary interconnect conductive layer 40 may improve the current uniformity along the electrochemically inactive cell (or active cell, as appropriate) in the in the direction of the fuel cell tube width. In some examples, secondary interconnect 34 may contact secondary interconnect conductive layer 40 across substantially the entire width of secondary interconnect conductive layer 40 in the direction of the fuel cell tube width. In some examples, secondary interconnect 34 may contact secondary interconnect conductive layer 40 across small portion of the width of secondary interconnect conductive layer 40 in the direction of the fuel cell tube width. For example, the secondary interconnect 34 may contact less than 10 millimeters of the total width of secondary interconnect conductive layer 40, wherein the width is considered from one fuel cell tube edge to the other edge (i.e., perpendicular to the length of the fuel cell channels), or less than 5 millimeters, or less than 1 millimeter. In some embodiments, the secondary interconnect 34 with or without the conducting paste 36 may have a width and thickness that achieve the conductance required of the system.
The electrochemically inactive cells of
In some examples, an electrochemically inactive cell is disposed adjacent to and electrically coupled to an anode of a fuel cell. In some examples, the electrochemically inactive cell is disposed adjacent to and electrically coupled to a cathode of a fuel cell.
In some examples, secondary interconnect 34a and secondary interconnect 34b may be electrically coupled to one another. In some examples, secondary interconnects 34a, 34b may be the same wire. In some examples, secondary interconnect 34a and secondary interconnect 34b may be mechanically joined, soldered, or otherwise electrically coupled. In this way, the plurality of fuel cells on top side 60a and the plurality of fuel cells on bottom side 60b may be electrically connected. In some examples, the plurality of fuel cells on top side 60a and the plurality of fuel cells on bottom side 60b may be electrically connected in series. In some examples, the plurality of fuel cells on top side 60a and the plurality of fuel cells on bottom side 60b may be electrically connected in parallel.
In some examples, the tube edge (not shown in
In some examples, the fuel cell tube may include at least two fuel cells on top side 60a and at least two fuel cells on bottom side 60b. In some examples, the fuel cell tube may include 100 or 50-60 fuel cells on top side 60a and 100, or 50-60, of fuel cells on bottom side 60b. In some examples, the fuel cell tube may include more than one thousand fuel cells on top side 60a and more than one thousand fuel cells on bottom side 60b.
In some examples, secondary interconnect conductive layer 40a, 40b may be disposed on an electrochemically active cell in accordance with, for example, the examples as described in
In some examples, secondary interconnect 34 may be bonded to a bonding site defined by bonding paste 36 on secondary interconnect conductive layer 40 and extend over the boundary defined by substrate 14. For example, cathode-side secondary interconnect 34a may be bonded to a bonding site defined by cathode-side bonding paste 36a on cathode-side secondary interconnect conductive layer 40a and extend over the boundary defined by substrate 14. Similarly, for example, anode-side secondary interconnect 34b may be bonded to a bonding site defined by anode-side bonding paste 36b on anode-side secondary interconnect conductive layer 40b and extend over the boundary defined by substrate 14.
In some examples, secondary interconnect conductive layer 40a, 40b may be disposed on an electrochemically active cell in accordance with, for example, the examples as described in
In some examples, secondary interconnect conductive layer 40 may extend over the boundary defined cathode conductive layer 30 or electrochemically inactive cell 50 and may extend proximate to and over a boundary defined by substrate 14 (i.e. the fuel cell tube edge). For example, cathode-side secondary interconnect conductive layer 40a extend over the boundary defined by cathode conductive layer 30a and may extend proximate to and over a boundary defined by substrate 14. Similarly, for example, anode-side secondary interconnect conductive layer 40b extend over the boundary defined by electrochemically inactive cell 50 and may extend proximate to and over a boundary defined by substrate 14. In embodiments wherein the SIC layer 40 is extended beyond the boundary defined by an electrochemical active or inactive cell, the SIC layer 40 may be deposited on top of a sealing glass configured to prevent the migration of H2 to and through the SIC layer 40.
Various experiments were carried out to evaluate one or more aspects of example fuel cell systems in accordance with the disclosure. However, examples of the disclosure are not limited to the experimental fuel cell systems.
In one instance, a fuel cell system in accordance with an example of the present disclosure was constructed by disposing fuel cells on a substrate, the fuel cell system including a plurality of fuel cells electrically coupled and connected in series with primary interconnects, and a terminal fuel cell on one end of the fuel cell tube including a dense barrier, an electrolyte disposed on the dense barrier, a cathode conductive layer disposed on the electrolyte, and a secondary interconnect wire constructed of Pd disposed on the cathode conductive layer, the secondary interconnect wire bonded to the cathode conductive layer with a Pd-based bonding paste. The dense barrier and electrolyte were configured to inhibit the flow of hydrogen from the fuel channel to the secondary interconnect. The fuel cell system was operated for approximately 2,400 hours. After operation, the Pd secondary interconnect wire microstructure was analyzed.
In another instance, a fuel cell system in accordance with the present disclosure was constructed by disposing fuel cells on a substrate, the fuel cell system including a plurality of fuel cells, one on a top surface and one on a bottom surface of a substrate/tube, electrically coupled and connected in series with primary interconnects, two secondary interconnect conductive layers disposed on each of an electrochemically inactive cell (“anode side”) and an electrochemically active cathode cell (“cathode side”), two secondary interconnect wires each bonded with conductive bonding paste to opposing edges on the upper surface of the secondary interconnect conductive layer disposed on the electrochemically inactive cell (anode side), and two secondary interconnect wires each bonded with conductive bonding paste to opposing edges on the upper surface of the secondary interconnect conductive layer disposed on the electrochemically active cell (cathode side). The respective SIC wires at each end and edge were bonded together to electrically couple the fuel cells on the top and bottom surfaces. The fuel cell system was operated up to approximately 17,520 hours with stable SIC wires that showed no significant microstructural change.
In another instance, a fuel cell system including fuel cell bundles in accordance with the present disclosure were operated for approximately 4,000 hours with no significant microstructure change in the secondary interconnect.
In another instance, a fuel cell system including fuel cell blocks in accordance with an example of the present disclosure were operated for approximately 3,000 hours with no significant microstructure change in the secondary interconnect.
The improved SIC wire and fuel cell system power output illustrated in
Various examples of the invention have been described. These and other examples are within the scope of the following claims.
Claims
1. A segmented-in-series solid oxide fuel cell system comprising:
- a fuel cell tube comprising: a substrate having a major surface; a fuel channel separated from said major surface by said substrate; a first and second electrochemically active fuel cells disposed on said major surface, each of said electrochemically active fuel cells comprising: an anode; a cathode; and an electrolyte disposed between said anode and said cathode; a primary interconnect electrically coupling the anode of said first electrochemically active fuel cell to the cathode of said second electrochemically active fuel cell; an electrochemically inactive cell disposed on said major surface, said electrochemically inactive cell comprising a conductive layer electrically coupled to the second electrochemically active fuel cell; and a secondary interconnect electrically coupled to said conductive layer of said electrochemically inactive cell,
- wherein said electrochemically inactive cell is configured to inhibit migration of hydrogen from said fuel channel to said secondary interconnect.
2. The fuel cell system of claim 1 wherein said conductive layer of said electrochemically inactive cell is electrically coupled to the anode of said second electrochemically active fuel cell.
3. The fuel cell system of claim 2 further comprising a second primary interconnect electrically coupling the conductive layer of said electrochemically inactive cell and the anode of said second electrochemically active fuel cell.
4. The fuel cell system of claim 2 wherein said electrochemically inactive cell further comprises a second conductive layer disposed between said secondary interconnect and said conductive layer.
5. The fuel cell system of claim 2 wherein said second conductive layer comprises a precious metal and a ceramic.
6. The fuel cell system of claim 2 wherein said electrochemically inactive cell further comprises an electrolyte disposed between said conductive layer and said major surface of said substrate.
7. The fuel cell system of claim 6 wherein said electrochemically inactive cell further comprises a second conductive layer disposed between said secondary interconnect and said conductive layer.
8. The fuel cell system of claim 6 wherein said electrochemically inactive cell further comprises a dense barrier disposed between the electrolyte and said major surface of said substrate.
9. The fuel cell system of claim 8 wherein said electrochemically inactive cell further comprises a second conductive layer disposed between said secondary interconnect and said conductive layer.
10. The fuel cell system of claim 2 wherein said electrochemically inactive cell further comprises a dense barrier disposed between said conductive layer and said major surface of said substrate.
11. The fuel cell system of claim 10 wherein said electrochemically inactive cell further comprises a second conductive layer disposed between said secondary interconnect and said conductive layer.
12. The fuel cell system of claim 2 wherein said secondary interconnect is at least partly buried by a conductive bonding paste.
13. The fuel cell system of claim 2 wherein said secondary interconnect comprises a palladium wire.
14. The fuel cell system of claim 2 wherein said conductive layer comprises a precious metal and a ceramic.
15. The fuel cell system of claim 2 wherein each of said electrochemically active fuel cells further comprises a cathode conductive layer electrically coupled to said cathode, and wherein the conductive layer of said electrochemically inactive cell is formed from the same material as each of said cathode conductive layers.
16. The fuel cell system of claim 1 wherein said secondary interconnect is at least partly buried by a conductive bonding paste.
17. The fuel cell system of claim 1 wherein said secondary interconnect comprises a palladium wire.
18. The fuel cell system of claim 1 wherein said conductive layer comprises a precious metal and a ceramic.
19. A segmented-in-series fuel cell system comprising:
- a substrate having a first major surface second major surface; a fuel channel disposed between the first and second major surfaces, wherein the fuel channel is separated from the first and second major surfaces by the substrate; a first and second electrochemically active fuel cells disposed on the first major surface and a third and fourth electrochemically active fuel cells disposed on the second major surface, each of said electrochemically active fuel cells comprising: an anode; a cathode; and an electrolyte disposed between said anode and said cathode; a first primary interconnect electrically coupling the anode of the first electrochemically active fuel cell to the cathode of the second electrochemically active fuel cell; a second primary interconnect electrically coupling the anode of the third electrochemically active fuel cell to the cathode of the fourth electrochemically active fuel cell; a first electrochemically inactive cell disposed on the first major surface and a second electrochemically inactive cell disposed on the second major surface, each of the electrochemically inactive cells comprising a conductive layer electrically coupled to at least one of the electrochemically active fuel cells; and a secondary interconnect electrically coupled to the conductive layer of the first and second electrochemically inactive cells,
- wherein the electrochemically inactive cells are configured to inhibit migration of hydrogen from the fuel channel to the secondary interconnect.
20. A fuel cell tube comprising:
- a substrate having a major surface;
- a fuel channel separated from the major surface by the substrate;
- at least one electrochemically active cell disposed on the major surface comprising: an anode; a cathode; and an electrolyte disposed between the anode and the cathode;
- an electrochemically inactive cell disposed on the major surface, the electrochemically inactive cell comprising: a conductive layer; an electrolyte disposed between said conductive layer and the major surface of said substrate; and a dense barrier disposed between the electrolyte and the major surface of said substrate; and
- a primary interconnect electrically coupling the anode of the electrochemically active cell and the conductive layer; and
- a secondary interconnect comprising palladium electrically coupled to the conductive layer of the electrochemically inactive cell, wherein the secondary interconnect is at least partly buried by a conductive bonding paste.
Type: Application
Filed: Nov 17, 2017
Publication Date: May 23, 2019
Applicant: LG Fuel Cell Systems, Inc. (North Canton, OH)
Inventors: Zhien Liu (Canal Fulton, OH), Rich Goettler (Medina, OH), Gerry Agnew (Uttoxeter), Peter Dixon (Derby)
Application Number: 15/816,937